|A cryptocurrency is digital money. There are many cryptocurrencies, just like there are many currencies like the Dollar, the Euro, and the Ruble.|
Each cryptocurrency is running on its own blockchain, because for every currency, you need a different record of transactions. Imagine I had one Dollar and one Euro, and I spend my Dollar. The Dollar blockchain records this transaction, so that it knows the new owner and that I don’t have my dollar anymore. On the other hand, this would not affect the blockchain for all the Euros.
If you own 1 ZEN, this means there is a transaction recorded on the blockchain where you received one ZEN. This transaction is your ZEN.